Bioactive materials for killing or inhibiting the growth and/or proliferation/spreading of bacteria, fungi, and other microorganisms have long been sought and employed in society. Their use dates back centuries, if not thousands of years. Early applications had ranged from pharmaceutical or health related applications to disinfectant and purification applications and more. More recent applications include a whole host of uses, with the largest use, by volume, seen in the agricultural industry. Perhaps one of the earliest bioactive materials was metallic silver and, subsequently, silver salts.
While early bioactive agents were most often metals and simple metal salts, modern science and chemical synthesis has enabled the development and production of synthetic agents, most often organic and organometallic agents, for antibacterial, antifungal and other like applications. Indeed, for many applications, especially pharmaceutical applications, the organic agents have, for the most part, eclipsed the use of inorganic bioactive agents. While inorganic and organometallic materials still command a significant market share of the agrichemical business, their use is limited due to their health and safety concerns, especially from an environment perspective.
Despite the great success and huge market share/volume commanded by organic pharmaceutical, antibacterial and agrochemical agents, they have not come without cost and consequences. In all areas of applications, a marked and growing trend has emerged: namely the manifestation and spreading of a resistance to such organic agents in most all, if not all, microorganisms. While this resistance is neither universal nor complete, it is growing and involves more and more organic agents. Furthermore, as their resistance grows, so too does their apparent virulence as well as their ability to quickly adapt to and manifest resistance to new bioactive agents and combinations thereof. In this respect, we are all well aware of the growing resistance of bacteria, especially pathogenic bacteria, to traditional pharmaceutical agents and the subsequent appearance of what are commonly referred to as superbugs: pathogenic bacteria that show strong resistance to traditional organic antibacterial and pharmaceutical agents. The same trend has been seen in the agrichemical industry where, for example, despite the great fanfare and promise behind the introduction of strobilurin fungicides in the mid-1990s, resistance had been found after just a couple years use in certain applications.
And, whether a direct or indirect consequence of the appearance of superbugs and/or the growing awareness of the ease by which bacteria can spread combined with an increasing concern for potentially pandemic diseases such as SARS and Bird Flu, we have become a population that is more and more pre-occupied with hygiene and general cleanliness. Consequently, there has been a huge proliferation and exponential growth in the widespread and indiscriminate use and application of cleansers and disinfectants that contain organic antimicrobial agents as well as in the production, marketing and use of a whole host of consumer products having one or more antimicrobial agents incorporated therein, all in an effort to ward off exposure to bacteria and, especially, superbugs. However, this indiscriminate use of organic agents has come with, or at least presents the possibility for, an overall increase in antimicrobial resistant organisms. By eradicating the weaker organisms, the stronger and, most often more damaging, organisms are left.
Such concerns, however, are not limited to our living environment, but also arise with respect to our food supply as well. Specifically, while resistance is certainly of great concern, perhaps and even greater concern is the human and environmental toll associated with the widespread use of antimicrobial agents: not just organic but inorganic, especially metals, as well. For more than half a century now, more and more scientific literature has appeared correlating long-term exposure to (direct and indirect) and use of organic agrichemicals to various diseases and teratogenic, mutanogenic, and other adverse health consequences in animals and, more importantly, the human population. Perhaps the watershed of this awareness is represented by the outcry relating to the use of DDT and like pesticide agents in the 1960s. However, such concerns are not limited to the organic pesticides: indeed, heavy metals, while extremely effective as or as a component of agrichemical agents, present equally troublesome issues.
Generally speaking, agrichemicals have long been under close scrutiny owing to known and increasing correlation between their use and/or exposure and the appearance of birth defects, cancer, and other diseases, not just in humans, but in plants and animals generally. Exposure routes are plenty with one of the chief exposure routes being water supplies that have or may become contaminated with such agrichemicals due to their and/or their by-product's solubility and long half-lives. Another exposure source concern is inhalation from dust blown up from the fields, from wayward aerosols and/or particulates during aerial spraying and dusting, respectively, and from exposure to the clothing of workers who, themselves, were exposed in the fields or during application.
While the foregoing present significant exposure concerns, perhaps the greatest exposure route, simply because it affects all people wherever they are located, is the food chain. For decades now, we've been challenged to limit the consumption of certain fish due to heavy metal, especially mercury, bioaccumulation. Similarly, we've seen one agrichemical after another pulled from use or more severely restricted in its use owing to the appearance of certain human health concerns and a concomitant public outcry. For example, in the late 1980's, the use of Alar, a very widely used and very beneficial agrichemical, on apples was “voluntarily” discontinued due to increasing health concerns pertaining to residual amounts of the agrichemical and/or its by-products in the apples and in apple juice produced from the treated apples. Consequently, crop yields and, more importantly, the esthetic look and shelf-life of the apple crops fell. Similar consequences have befallen more and more agrichemicals, putting more stress on the remaining agrichemicals to carry the weight, especially as mankind looks to generate more and more crop from a given land area.
While there is a growing trend and push to grow organically and eliminate agrichemicals, such options are not practical and, more importantly, result in crops that have a shorter shelf life and, in many instances, do not look as fresh and appetizing as those that have benefited from agrichemicals, either during the growing process or as a pre-harvest/post-harvest treatment. Additionally, with the agricultural economy now a world-wide economy with fruits and vegetables being flown all over the world to enable year-round enjoyment of seasonal products, there is a growing need to improve shell life and ward off spoilage. Furthermore, and perhaps more importantly, there is an ever growing concern with the safety of our foods and foodstuffs: particularly from a food borne illness perspective. In particular, several significant incidents in the United States involving pathogenic bacteria contaminated spinach and green leaf products led to several deaths and serious illnesses as well as the loss of hundreds of millions of dollars in crop destruction and product recalls. Such concerns are not just with respect to agriculturally grown foods and foodstuffs, but apply to protein based food and feed products, including fish, poultry, eggs, meats, and the like, as well.
In light of the foregoing, it is clear that the agricultural industry, indeed the food supply chain, is in a huge quandary, use pre-harvest and post-harvest agrichemicals to preserve and protect food products from spoilage and bacterial contamination or protect the environment and food chain from agrichemical build-up and contamination and microorganism resistance. With other food products, especially protein products, again there is the desire for long shelf-life and reduced spoilage and bacterial contamination while avoiding or at least minimizing any environmental and/or food contamination with preservative or other agrichemical agents.
Thus, there is a need for pre-harvest treatments for food crops that minimize any release or exposure of harmful agrichemical actives or agents, especially any that may tend to bio-accumulate, into the environment and/or to those applying the same.
Similarly, there is a need for post-harvest treatments for food crops that have minimal risk of human health exposure and/or exposure related concerns.
Similarly, there is a continuing need for food preservative agents that can be employed for inhibiting spoilage, especially that arising from microorganisms, of foods and food stuffs, as well as feed crops.
In particular, there is a need for inorganic antimicrobial, antifungal, antibacterial, etc., agents that may be used universally, or nearly so, on food crops and products without concern, or certainly with reduced concern, for environmental contamination and toxicity.
Similarly, there is a need for inorganic agents that are stable and easy to use, and provide good short term and, preferably, longer term efficacy as compared to many of the current short lived organic agents.